With the introduction of quantum computing on the horizon, computer security organizations are stepping up research and development to defend against a new kind of computer power. Quantum computers pose a very real threat to the global information technology infrastructure of today. Many security implementations in use based on the difficulty for modern-day computers to perform large integer factorization. Utilizing a specialized algorithm such as mathematician Peter Shor’s, a quantum computer can compute large integer factoring in polynomial time versus classical computing’s sub-exponential time. This theoretical exponential increase in computing speed has prompted computer security experts around the world to begin preparing by devising new and improved cryptography methods. If the proper measures are not in place by the time full-scale quantum computers produced, the world’s governments and major enterprises could suffer from security breaches and the loss of massive amounts of encrypted data

1. QUANTUM
COMPUTER IN
CRYPTOGRAPHY
AKSHAY MAHADEO SHELAKE
(T.Y.B.SC–COMP. SCI.)

2. Introduction
• What is Quantum Computer?
• The History of Quantum Computing
• What is Cryptography ?
• What are used todays Cryptography technology?
• Computer Security Organizations and Quantum Computing

3. What is Quantum Computer ?
• A quantum computer is a machine that performs calculations based
on the laws of quantum mechanics, which is the behavior of particles
at the sub-atomic level.

4. The History of Quantum Computing
The idea of a quantum computer began in the early 1980s and was
conceived by
• Paul Benioff
• Charles Bennett
• David Deutsch
• Richard Feynman
• Yuri Manin

6. classical computers VS quantum computers
The essence of the difference between
classical computers and quantum computers
is in the way information is stored and processed.
In classical computers, information is represented on macroscopic level by bits, which can take one of the two
values
0 or 1
In quantum computers, information is represented on microscopic level using qubits, (quantum bits) which can
take on any from the following uncountable many values
 | 0  + b | 1 
where , b are arbitrary complex numbers such that
|  | 2 + | b | 2 = 1.

7. Figure 3:Two-slit experiment
Figure 4:Two-slit experiment with an observation
Figure 1: Experiment with bullets
Figure 2: Experiments with waves
Classical Experiments VS Quantum Experiments

8. a,b  G , ak = b , find k
Discrete logarithms (basis of DH crypto, including ECC):
Integer Factorization (basis of RSA cryptography):
Given N=pq, find p and q.
Quantum Algorithms

9. Computational Complexity Comparison
(in terms of number of group multiplications for n-bit inputs)

10. Scaling of number field sieve
(NFS) on classical computers
and Shor’s algorithm for
factoring on a quantum
computer, using Beckman-
Chari-Devabhaktuni-Preskill
modular exponentiation with
various clock rates. Both
horizontal and vertical axes
are log scale.The horizontal
axis is the size of the number
being factored (Van Meter,
Itoh, & Ladd, 2005).

11. What is Cryptography ?
Transmitting information with access restricted to the intended recipient
even if the message is intercepted by others.
Cryptography is of increasing importance in our technological age using
broadcast, network communications, Internet ,e-mail, cell phones which
may transmit sensitive information related to finances, politics, business
and private confidential matters

12. CLASSICAL versus QUANTUM CRYPTOGRAPHY
Security of classical cryptography is based on unproven assumptions of
computational complexity (and it can be jeopardize by progress in algorithms and/or
technology).
Security of quantum cryptography is based on laws of quantum physics that allow to
build systems where undetectable eavesdropping is impossible
Since classical cryptography is volnurable to technological improvements it has to be
designed in such a way that a secret is secure with respect to future technology,
during the whole period in which the secrecy is required.
Quantum key generation, on the other hand, needs to be designed only to be secure
against technology available at the moment of key generation.

13. public-key Cryptography
• Encryption of data for many IT systems today relies on public-key
cryptography. The concept of public-key cryptography was introduced by
Whitfield Diffie and Martin Hellman in 1976
• This new method of encryption had two main purposes, encryption and
digital signatures. It entails that each person (or communicating system) gets
a pair of keys, one was dubbed the public key and the other was named the
private key.
• The public key is shared between the two parties and is used for identifying
the end-user while the private key remains a secret and is never transmitted.
Encrypted information is sent using the public key to identify the source but
only a receiver that possesses the private key is able to decode the message.
Unfortunately, the private key, while kept a secret from prying eyes, is linked
to the public key through a mathematical algorithm

14. Company's developing QKD System
• In 2002 - Swiss company called id Quantique
• In 2003 -American company called MagiQ
Technologies

15. Methods of Cryptography in Quantum Computer
Cryptographers are discussing alternatives to today’s methods and have agreed that
there are four major candidates that would provide immunity from a quantum computer
attack.
The four possible replacement methods include:
- error-correcting codes
- hash-functions
- lattice cryptography systems
- multivariate public-key cryptography system

16. Commercial
quantum key
distribution
products exist
Current State of Affairs

17. Current fiber-
based distance
record: 200 km
(Takesue et al)
Current State of Affairs

18. Demonstrated free-space link: 10 km
Current State of Affairs

19. CONCLUSION
Quantum cryptography ensure secure communication by providing security based
on the fundamental law of physics, intend of the current state of mathematical
algorithms or computing technology unlike classical encryption algorithm quantum
cryptography does not depend factoring large integers into primes but on the
fundamental principles of quantum physics. Quantum cryptography is more secure,
because an intruder is not able to replicate the photon to recreate the key.
Integrating QKD inTLS protocol will ensure financial transaction. Instead of using
RSA, inTLS protocol .We can use Quantum Cryptography securely exchange the
secret data and avoid an attack of intruder

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